Leclerc finished just over a tenth of a second clear of George Russell, who also delivered promising pace in his upgraded Mercedes.
Leclerc finished just over a tenth of a second clear of George Russell, who also delivered promising pace in his upgraded Mercedes.
Carlos Sainz was marginally behind Russell to take third in the other Ferrari, but world championship leader Max Verstappen could only manage fifth behind his Red Bull team-mate Sergio Perez.
In perhaps the most highly-anticipated Formula 1 practice session of the season so far with Red Bull, Ferrari and Mercedes all bringing new parts, Leclerc was able to thrill the Tifosi by providing a performance that suggests Verstappen will continue to be challenged throughout the weekend.
The Dutchman, who holds a 33-point world championship lead as he chases a fourth successive drivers’ title, grew increasingly frustrated as he went off track twice when attempting flying laps in the closing stages of the session.
After claiming his maiden F1 victory two weeks ago as McLaren rolled out their own major upgrade package in Miami, Lando Norris was eighth ahead of team-mate Oscar Piastri.
Yuki Tsunoda took an encouraging sixth for RB, with Lewis Hamilton seventh after going off track several times as he struggled with the handling of his Mercedes.
Ferrari team principal Fred Vasseur has repeatedly preached that the Italian squad must apply pressure to a Red Bull team that have had things all their own way since midway through the 2022 season.
The merits of that approach appeared to be evident in Friday’s opening session as Verstappen, after being beaten by Norris in Miami, grew increasingly frustrated at the imperfect handling of his car.
Despite a return to F1’s traditional format of three practice sessions before Saturday’s qualifying after two successive Sprint weekends, the Dutchman did not appear to be in patient mood as he complained of a lack of a grip.